This application relates generally to gas turbine engines, and more particularly, to a bearing assembly used within a gas turbine engine and a method of monitoring same.
Gas turbine engines typically include a fan assembly, a core engine including a compressor, a combustor, and a first turbine, i.e. high-pressure turbine, and a second or low-pressure turbine that is coupled axially aft of the core gas turbine engine. The fan assembly and the low pressure turbine are coupled together using a first shaft, and the compressor and the high-pressure turbine are coupled together using a second shaft. At least one known gas turbine engine also include a differential bearing, i.e. inter-shaft bearing, that is coupled between the first and second shafts, respectively.
During operation, failure of a bearing assembly may result in an In Flight Shut Down (IFSD), and/or an Unscheduled Engine Removal (UER). Therefore, at least one known gas turbine engine includes a magnetic chip detection system that includes a magnet that attracts metallic debris that is created during bearing contact fatigue failures such as, but not limited to micro-spalling, peeling, skidding, indentations, and/or smearing. More specifically, magnetic chip detectors facilitate identifying the presence and quantity of metallic debris in a gas turbine lube oil scavenge line. In addition, a scanning electron microscope (SEM) may be used to determine the source of the metallic debris. However, known magnetic chip detection systems and SEM analysis systems can only detect a bearing spalling that has already occurred.
At least one known gas turbine engine also includes a vibration measurement system that transmits relatively high frequency acoustic emissions through the bearing to verify a bearing failure caused by bearing contact fatigue that has previously occurred. However, known vibration measurement systems may not be able to successfully identify the bearing failure if the transmitted signal is degraded when passed through a lubricant film that is used to lubricate the bearing. Therefore, identifying the bearing component frequencies among a plurality of engine operating frequencies may be relatively difficult. Accordingly, known systems are generally not effective in detecting initial bearing flaws and/or defects that may result in bearing spalling, in monitoring bearing damage and/or spall propagation, or in assessing the overall bearing damage including multi-spall initiations and progression.